Insulin Glargine
Brand names: Lantus, Basaglar, Toujeo
Class: 🩸 Antidiabetics
For the FNP boards, insulin glargine is the basal insulin that runs in the background of any insulin regimen. It is a long-acting analog with a relatively flat 24-hour profile — onset around 1 hour, no real peak, duration up to 24 hours — used once daily in T1DM (with mealtime bolus) and in T2DM when oral agents and GLP-1 agonists are insufficient. Starting dose is roughly 0.1–0.2 units/kg/day, titrated by fasting glucose. The dose-limiting harm is nocturnal hypoglycemia. Glargine is acidic and cannot be mixed in syringe with other insulins. Toujeo is U-300 glargine — same drug, three times more concentrated, with a slightly flatter profile in some patients.
✅ Indications
Basal insulin for T1DM and T2DM requiring insulin.
⚙️ Mechanism of Action
Long-acting (basal) insulin analog — ~24 hour steady-state coverage.
📏 Dosing
Once daily at same time. Start 0.1–0.2 units/kg/day; titrate by fasting BG.
🚫 Contraindications
Hypoglycemia episodes.
⚠️ Adverse Effects
Hypoglycemia, weight gain, injection-site reactions, lipohypertrophy.
🔬 Monitoring
Fasting BG (self-monitoring), A1c, weight, signs of hypoglycemia.
💎 Board Pearls
- 🕐 Flat 24-hour profile (vs NPH which peaks at 4–12 h).
- 🚫 NEVER mix glargine with other insulins in the same syringe (acidic pH → precipitation).
- 💡 "Bed-time Lantus" is the common starting regimen — adjust by fasting BG.
Practice Questions
The nurse practitioner is educating a patient newly prescribed insulin glargine (Lantus) once daily at bedtime, in addition to pre-meal insulin lispro. Which instruction regarding administration of insulin glargine is MOST accurate?
Related Drugs in This Class
- Metformin — Glucophage, Fortamet, Glumetza
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- Empagliflozin — Jardiance
- Semaglutide — Ozempic (injectable), Wegovy (weight), Rybelsus (oral)
- Insulin Lispro — Humalog
Sources
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